Ligases serve as:

Options

A. molecular glue that help in sealing gaps in DNA fragments
B. breaking hydrogen-bond between base pairs
C. uncoiling of DNA strand
D. synthesis of complementary DNA

Answer

**Step-by-Step Solution:**

1. **Understanding Ligases**: Ligases are a type of enzyme that play a crucial role in molecular biology. They are primarily responsible for joining two DNA fragments together.

2. **Identifying the Function of Ligases**: The main function of ligases is to act as "molecular glue." This means they help in sealing gaps between DNA fragments, ensuring that the DNA strands are continuous and intact.

3. **Evaluating the Options**:
- **Option A**: "Molecular glue that help in filling gaps in DNA fragments" - This is correct as ligases join DNA fragments.
- **Option B**: "Breaking hydrogen bond between base pairs" - This is incorrect. Ligases do not break bonds; they join fragments.
- **Option C**: "Uncoiling of DNA strands" - This is also incorrect. Uncoiling is done by enzymes called topoisomerases, not ligases.
- **Option D**: "Synthesis of DNA" - This is misleading. While ligases are involved in the process of DNA manipulation, they do not synthesize DNA directly.

4. **Conclusion**: Based on the evaluation of the options, the correct answer is that ligases serve as "molecular glue that help in filling gaps in DNA fragments."

**Final Answer**: Ligases serve as molecular glue that help in filling gaps in DNA fragments.

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